angles

import ampform_dpd.angles

Formulate expressions for scattering and alignment angles.

formulate_scattering_angle(state_id: int, sibling_id: int) → tuple[Symbol, acos]

Formulate the scattering angle in the rest frame of the resonance.

Compute the \(\theta_{ij}\) scattering angle as formulated in Eq (A1) in the DPD paper. The angle is that between particle \(i\) and spectator particle \(k\) in the rest frame of the isobar resonance \((ij)\).

formulate_theta_hat_angle(isobar_id: int, aligned_subsystem: int) → tuple[Symbol, acos]

Formulate an expression for \(\hat\theta_{i(j)}\).

formulate_zeta_angle(rotated_state: int, aligned_subsystem: int, reference_subsystem: int) → tuple[Symbol, acos]

Formulate an expression for the alignment angle \(\zeta^i_{j(k)}\).